The original buccal absorption test was introduced by Beckett and Triggs in 196730. An oral solution of the drug is held in the mouth without swallowing. After a measured period, the mouth is emptied and rinsed, and the amount of unabsorbed drug remaining is assayed. This method has several disadvantages, primarily that an absorption-time profile must be built up from several separate experiments. The drug concentration also changes due to salivary secretion31 and swallowing; this latter can be compensated by using a non-absorbed internal marker32. More recently Tucker33 has described a modification of the method which uses continuous oral sampling so that repeated experiments are not necessary. All these procedures suffer from the drawback that only absorption from the whole oral epithelia can be measured, and if the absorption is low, the precision of the method is poor.
To measure the absorption of drug from a specific region, a small filter paper disc soaked in drug can be applied to the mucosa. This technique has been used to measure the uptake or loss of water, sodium and potassium ions34. A more elegant method of measuring drug absorption from the various regions is a chamber through which drug solution can be circulated which can be applied to various regions of the mucosa35. This has the advantage that both plasma levels and effluent from the chamber can be analysed for drug content.
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